Image reading apparatus, image forming apparatus, control method, and program that accounts for time intervals from one document to another document

ABSTRACT

An image reading apparatus is provided which allows a reading device fixed at a reading position to read images from a document while transporting the document. The apparatus includes a correcting unit adapted to perform correction processing associated with image reading performed by the reading device; a calculating unit adapted to calculate a time interval from one document to the next document that are being transported; a scheduling unit adapted to divide the correction processing into a plurality of steps and schedule the execution of the steps on the basis of the calculated time interval; and an executing unit adapted to sequentially execute the steps scheduled by the scheduling unit every time a document passes through the reading position.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/271,459, filed on Nov. 10, 2005, entitled “IMAGE READINGAPPARATUS, IMAGE FORMING APPARATUS, CONTROL METHOD, AND PROGRAM”, thecontent of which is expressly incorporated by reference herein in itsentirety. This application also claims the benefit of JapaneseApplication No. 2004-332373 filed Nov. 16, 2004, which is herebyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus for readingimages from a document, a control method for the image readingapparatus, and a program for having a computer execute the controlmethod.

2. Description of the Related Art

Some known image reading apparatuses with an automatic document feeder(hereinafter “ADF”) have a mode called a “skimming mode” that is areading mode using the ADF. In the skimming mode, an image readingapparatus allows its document reader fixed at a predetermined readingposition to read images from a document while allowing its ADF to feedthe document at a constant speed.

To maintain the quality of images read from a document, some imagereading apparatuses having a skimming mode perform a predeterminedoperation during intervals between documents being fed. For example,Japanese Patent Laid-Open No. 2002-300394 discloses an image readingapparatus that monitors fluctuations in lamp intensity during intervalsbetween reading individual documents, and adjusts the lamp intensity ifthe amount of fluctuations in lamp intensity exceeds a certain level.

In another instance, Japanese Patent Laid-Open No. 2000-209403 disclosesan image reading apparatus having a skimming mode, which prohibits theexecution of correction processing during intervals between readingindividual documents if the distance between the document currentlypassing through a reading position and the subsequent document fallsbelow a certain level.

To read a document with images on both sides, many image readingapparatuses having a skimming mode provide an ADF that allows thedocument to pass through a reading position three times. Specifically,after the first surface (hereinafter called front side) is read, thedocument is reversed. Then, after the second surface (hereinafter calledback side) is read, the document is reversed again so that all documentsare ejected consistently with the same side up (idle reverse ejection).

To increase productivity when a document with images on both sides isread, some image reading apparatuses with the above-described ADFprovide a high-speed double-side reading mode in which two documents aretransported along a transport path in the ADF. In the high-speeddouble-side reading mode, after the back side of the previous documentis read, the front side of the next document is read simultaneously withthe idle reverse ejection of the previous document. That is, the orderof a plurality of documents that pass through a reading point is asfollows: first document (front side)→first document (back side)→seconddocument (front side)→first document (idle reversal)→second document(back side)→third document (front side)→second document (idlereversal)→third document (back side)→. . . .

However if, as described above, the execution of correction processingduring intervals between reading individual documents is prohibited whenthe distance between the document currently passing through a readingposition and the subsequent document falls below a certain level,correction to the subsequent document may not be properly made. In otherwords, the known image reading apparatuses described above may not beable to produce high-quality read images from documents.

SUMMARY OF THE INVENTION

The present invention provides an image reading apparatus, a controlmethod, and a program (computer readable medium) that allow correctionto be performed even if the interval between a document currently beingread and the subsequent document is reduced, and are thus capable ofpreventing the quality of read images from being degraded.

According to a first aspect of the present invention, an image readingapparatus, allowing a reading device fixed at a reading position to readimages from a document while transporting the document, includes acorrecting unit adapted to perform correction processing associated withimage reading performed by the reading device; a calculating unitadapted to calculate a time interval from one document to the nextdocument that are being transported; a scheduling unit adapted to dividethe correction processing into a plurality of steps and schedule theexecution of the steps on the basis of the time interval calculated bythe calculating unit; and an executing unit adapted to sequentiallyexecute the steps scheduled by the scheduling unit every time a documentpasses through the reading position.

According to a second aspect of the present invention, an image formingapparatus includes the aforementioned image reading apparatus incombination with an image forming unit adapted to form images on a sheeton the basis of images read by the image reading apparatus.

According to a third aspect of the present invention, a control methodfor an image forming apparatus, allowing a reading device fixed at areading position to read images from a document while transporting thedocument, includes performing correction processing associated withimage reading performed by the reading device; calculating a timeinterval from one document to the next document that are beingtransported during reading in a selected reading mode; dividing thecorrection processing into a plurality of steps and scheduling theexecution of the steps on the basis of the time interval calculated bythe calculating step; and sequentially executing the steps scheduled bythe scheduling step every time a document passes through the readingposition.

According to a fourth aspect of the present invention, a program isprovided which causes a computer to execute the aforementioned control.In particular, a computer readable medium is provided which containscomputer-executable instructions for an image forming apparatus allowinga reading device fixed at a reading position to read images from adocument while transporting the document. The computer readable mediumincludes computer-executable instructions for performing correctionprocessing associated with image reading performed by the readingdevice; computer-executable instructions for calculating a time intervalfrom one document to the next document that are being transported duringreading in a selected reading mode; computer-executable instructions fordividing the correction processing into a plurality of steps andscheduling the execution of the steps on the basis of the time intervalcalculated by the calculating step; and computer-executable instructionsfor sequentially executing the steps scheduled by the scheduling stepevery time a document passes through the reading position.

Further embodiment, aspects and features of the present invention willbecome apparent from the following description of exemplary embodimentswith reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the structure of an exemplary image reading apparatusaccording to a first embodiment of the present invention.

FIG. 2 shows an exemplary drive system for an ADF of the image readingapparatus from FIG. 1.

FIG. 3 is a block diagram showing an exemplary architecture of a controlsystem for the ADF.

FIG. 4 is a block diagram showing an exemplary architecture of a readerof the image reading apparatus.

FIG. 5 is a block diagram showing an exemplary architecture of an imageprocessor of the reader.

FIG. 6 is a diagram showing a portion of an exemplary operation inhigh-speed double-side reading mode.

FIG. 7 is a diagram showing another portion of the operation inhigh-speed double-side reading mode.

FIG. 8 is a diagram showing still yet another portion of the operationin high-speed double-side reading mode.

FIG. 9 is a diagram showing another portion of the operation inhigh-speed double-side reading mode.

FIG. 10 is a diagram showing still yet another portion of the operationin high-speed double-side reading mode.

FIG. 11 is a diagram showing another portion of the operation inhigh-speed double-side reading mode.

FIG. 12 is a diagram showing still yet another portion of the operationin high-speed double-side reading mode.

FIG. 13 is a diagram showing another portion of the operation inhigh-speed double-side reading mode.

FIG. 14 is a block diagram showing a light-distribution fluctuationcorrection process and dust correction process in an inter-sheetcorrection processor of the reader.

FIG. 15 is a diagram for explaining light-intensity fluctuationcorrection, which is an aspect of the operations of inter-sheetcorrection processing.

FIG. 16 is a diagram for explaining light distribution correction, whichis another aspect of the operations of the inter-sheet correctionprocessing.

FIG. 17 is a diagram for explaining dust detection and dust counting,which is another aspect of the operations of the inter-sheet correctionprocessing.

FIGS. 18A and 18B are diagrams for explaining dust removal, which isanother aspect of the operations of the inter-sheet correctionprocessing.

FIG. 19 is a diagram for explaining the calculation of inter-sheetperiods.

FIG. 20 shows an example in which the processing of thelight-distribution fluctuation correction process and dust correctionprocess is divided into multiple steps by time period.

FIG. 21 shows an example of a schedule pattern table in which theinter-sheet correction processing is divided into steps by time period,on the basis of the minimum inter-sheet period.

FIG. 22 is a flowchart showing an exemplary process of the inter-sheetcorrection processing.

FIG. 23 is a flowchart continued from FIG. 22.

FIG. 24 is a flowchart showing an exemplary process of the inter-sheetcorrection processing in high-speed double-side reading mode.

FIG. 25 is a flowchart continued from FIG. 24.

DESCRIPTION OF THE EMBODIMENTS

Embodiments and various aspects of the present invention will now bedescribed with reference to the drawings.

First Exemplary Embodiment

FIG. 1 shows the structure of an exemplary image reading apparatusaccording to the first embodiment of the present invention. The imagereading apparatus includes an ADF 100 and a reader 200. The ADF 100includes a document tray 20, a pickup roller 1, a separator 2, a firstregistration roller 3, a second registration roller 4, a first transportroller 5, a second transport roller 6, a large roller 7, and an ejectionroller 8. The reader 200 includes an ADF glass platen (hereinafter“platen”) 201, a book platen 202, a lamp 203, a scanner unit 209,mirrors 204-206, a lens 207, and a charge-coupled device (CCD) sensor208.

The image reading apparatus of the present embodiment provides aplurality of reading modes, including a single-side reading mode, anormal double-side reading mode, and a high-speed double-side readingmode. The single-side reading mode allows the reading of one side of adocument transported along a document path of the ADF 100. The normaldouble-side reading mode allows the reading of both sides of a documenttransported along the document path of the ADF 100. In the high-speeddouble-side reading mode, after the back side of the first of twodocuments transported along the document path of the ADF 100 is read,the front side of the next document is read simultaneously with the idlereverse ejection of the first document.

The ADF 100 is a device that automatically feeds documents. From the topof a batch of documents S placed face up on the document tray 20, thepickup roller 1 driven by a paper feed clutch (CL) 9 sequentially feedsindividual documents into the separator 2. Then, the separator 2 havinga separation pad and a separation roller thereon with the document pathinterposed therebetween allows the documents to be transported one byone.

The reader 200 optically reads images from a document, photoelectricallyconverts reflected light from the document into electric signals, andinputs them as image data. The ADF platen 201 provided is for readingimages from a document while the ADF 100 feeds the document. The bookplaten 202 is provided for reading images from a document placedthereon. For reading images while the ADF 100 feeds a document, thescanner unit 209 is moved to a position under the ADF platen 201 andstopped such that the scanner unit 209 can read images while thedocument passes through a reading position R. To read images from adocument placed on the book platen 202, the scanner unit 209 is movedfrom a document-set reference position (not shown) in the sub-scanningdirection.

For reading images from a document, the lamp 203 of the scanner unit 209illuminates the document. Reflected light from the document is inputinto the CCD sensor 208 via mirrors 204 through 206 and a lens 207.Then, the CCD sensor 208 photoelectrically converts the reflected lightfrom the document into electric signals. Image signals are thusoutputted.

For reading images from the front side of a document with images on oneside (front side), the first registration roller 3 applies skewcorrection to the document that is being separately transported. Then,the second registration roller 4, the first transport roller 5, and thesecond transport roller 6 feed the document to the reading position R ona transport guide 16. Images on the front side of the document are readwhile the document passes through the reading position R. When thetrailing end of the document has passed through the reading position R,the document is nipped by the application of a voltage to a solenoid(SL) 22, and transported by the second transport roller 6, and ejectedface down onto a paper ejection tray 21.

For reading images from both sides of a document with images on bothsides (front side and back side), the first registration roller 3applies skew correction to the document that is being separatelytransported. Then, the second registration roller 4, the first transportroller 5, and the second transport roller 6 feed the document to thereading position R on the transport guide 16. Images on the front sideof the document are read while the document passes through the readingposition R. When the trailing end of the document has passed through thereading position R, the document is nipped by the application ofpressure to the solenoid 22 and transported by the second transportroller 6. Then, temporarily, the ejection roller 8 allows the trailingend of the document to move toward the paper ejection tray 21. When apaper ejection sensor 13 detects the trailing end of the document and isturned off, the transport of the document is stopped with the trailingend of the document nipped by the ejection roller 8.

After the switchback transport of the document, the second registrationroller 4 applied skew correction to the document again. Then, thesolenoid 22 is released and the second registration roller 4, the firsttransport roller 5, and the second transport roller 6 feed the documentto the reading position R. Images on the back side of the document areread while the document passes through the reading position R again.

If the second transport roller 6 and the ejection roller 8 directlyeject the document face up onto the paper ejection tray 21, the order ofthe faces of the document will differ from that of other documentsplaced on the document tray 20. Therefore, after images on the back sideof the document is read, the second transport roller 6 and the ejectionroller 8 allow the trailing end of the document to be sent toward thepaper ejection tray 21 again.

When the paper ejection sensor 13 detects the trailing end of thedocument and is turned off, the transport of the document is stoppedwith the trailing end of the document nipped by the ejection roller 8.After the switchback transport of the document, the second registrationroller 4, the first transport roller 5, and the second transport roller6 feed the document to the ejection roller 8, which then ejects thedocument face down onto the paper ejection tray 21. Although thedocument passes through the reading position R during this time period,images on the document are not read.

The image reading apparatus further includes an operating section and adisplay section (not shown). The user operates the operating section toissue a command for initiating a reading operation to the image readingapparatus, and to determine the settings of the various reading modes(single-side reading mode, normal double-side reading mode, andhigh-speed double-side reading mode). The display section displays theoperating status of the image reading apparatus, warning messages, andthe like.

FIG. 2 shows an exemplary drive system for the ADF 100 of the imagereading apparatus. A separation motor M1 drives the separator 2 (seeFIG. 1) and the first registration roller 3 (see FIG. 1). A paper feedmotor M2 drives the second registration roller 4 (see FIG. 1), the firsttransport roller 5 (see FIG. 1), and the second transport roller 6 (seeFIG. 1). A paper ejection motor M3 drives the ejection roller (seeFIG. 1) 8. In FIG. 2, rollers to be driven by the separation motor M1,the paper feed motor M2, and the paper ejection motor M3, respectively,are schematically enclosed by dashed rectangles.

FIG. 3 is a block diagram showing an exemplary architecture of a controlsystem for the ADF 100 of the image reading apparatus. The ADF 100includes a central processing unit (CPU) 800, a read-only memory (ROM)801, a random-access memory (RAM) 802, and output and input ports (notshown).

The CPU 800 controls each part of the ADF 100. According to a controlprogram stored in the ROM 801 connected to the CPU 800 via a bus, theCPU 800 controls the separation motor M1, the paper feed motor M2, thepaper ejection motor M3, a separation solenoid SL, and a paper feedclutch CL. At the same time, the CPU 800 performs serial communicationwith a CPU 1306 (see FIG. 4) of the reader 200 to send and receivecontrol data to and from the reader 200. The control program describedabove is stored in the ROM 801. Input data and work data is stored inthe RAM 802.

The separation motor M1, the paper feed motor M2, the paper ejectionmotor M3, the separation solenoid SL, and the paper feed clutch CL areconnected to output ports of CPU 800. A separation sensor 10 thatdetects a document separated by the separator 2, a registration sensor11 that detects a document near the first registration roller 3, and aread sensor 12 that detects a document near the first transport roller 5are connected to input ports of CPU 800. A paper ejection sensor 13 thatdetects a document near the ejection roller 8, a document sensor 14 thatdetects a document on the document tray 20, a document length sensor 15that detects the length of a document, and a document width sensor 810(not shown in FIG. 1) that detects the width of a document are alsoconnected to input ports of CPU 800.

FIG. 4 is a block diagram showing an exemplary architecture of thereader 200 of the image reading apparatus. The reader 200 includes animage processor 1302, an image memory 1303, an inter-sheet correctionprocessor 1304, a CPU 1306, a motor driver 1307, and a sensor-signalinput unit 1308.

The CPU 1306 controls each part of the reader 200, and is provided witha program storage ROM and work RAM (not shown). The CPU 1306 controlsthe reader 200 using the motor driver 1307 and the sensor-signal inputunit 1308. The motor driver 1307 drives an optical-system drive motorthat allows the scanner unit 209 to move in the sub-scanning direction.The sensor-signal input unit 1308 inputs signals outputted from varioussensors in the reader 200 into the CPU 1306.

On the basis of time intervals between individual documents beingtransported during reading in the reading modes described above, and onthe basis of time required for correction processing steps, theinter-sheet correction processor 1304 assigns the steps to time unitsthat fall within the time intervals between documents in the readingmodes. Then, the inter-sheet correction processor 1304 creates aschedule pattern table (see FIG. 21) for each of the reading modes suchthat all correction processing steps are executed in one or a pluralityof time intervals between documents. The inter-sheet correctionprocessor 1304 then performs inter-sheet correction processing. On thebasis of the control program described above, the inter-sheet correctionprocessor 1304 executes processing shown in the flowchart in FIGS. 22and 23 (first embodiment), and processing shown in the flowchart inFIGS. 24 and 25 (second embodiment).

Image data is stored in the image memory 1303. The image processor 1302converts image signals, which are formed into images on the CCD sensor208 via the lens 207 and the like, into digital image data, performsvarious image processing operations thereon, and writes the digitalimage data in the image memory 1303.

FIG. 5 is a block diagram showing the structure of the image processor1302 of the reader 200. The image processor 1302 includes an amplifiercircuit 1401, an analog-to-digital (A/D) converter 1402, and acorrection circuit 1403.

In the process of scanning images on a document, an analog image signalwith respect to each scanning line is output from the CCD sensor 208 andis input to the amplifier circuit 1401. The analog image signal isamplified by the amplifier circuit 1401 and converted into an 8-bitdigital image signal by the A/D converter 1402. Furthermore, on thebasis of inter-sheet correction data 1508 created in the inter-sheetcorrection processor 1304, the correction circuit 1403 performscorrection processing on the digital image signal. Then, image data iswritten into the image memory 1303. The processing described above iscarried out for all image areas on the document. Images read from thedocument are thus created.

Next, the overview of operations in high-speed double-side reading modeof the image reading apparatus will now be described with reference toFIGS. 6 to 13, and in particular, when images are read from twodocuments in high-speed double-side reading mode.

Beginning with FIG. 6, images on the front and back sides of the firstdocument are read. In the image reading for the front side of the firstdocument, when the trailing end of the first document has passed throughthe read sensor 12, the second document is separated by the separator 2from a batch of documents S on the document tray 20. After beingseparated, the second document is placed on standby at the position ofthe first registration roller 3.

As shown in FIG. 7, upon completion of the image reading for the frontside of the first document, the switchback transport of the firstdocument is performed along a switchback path, and images on the backside of the first document are read.

As shown in FIG. 8, when a predetermined time period has elapsed afterthe trailing end of the first document has passed through the secondregistration roller 4, the feeding of the second document that has beenon standby at the position of the first registration roller 3 starts.

Next, as shown in FIG. 9, after images on the back side of the firstdocument are read, a voltage is applied to the solenoid 22 and theejection roller 8 allows the first document to be transported toward thepaper ejection tray 21. At the same time, the second document istransported and the image reading on the front side of the seconddocument starts.

Then next, as shown in FIG. 10, for idle transport, the first documentis fed to the switchback path through switchback transport. After theimage reading on the front side of the second document starts, thesolenoid 22 is released by the time the leading end of the seconddocument reaches the ejection roller 8. This is on the condition thatthe leading end of the first document has passed through the secondregistration roller 4.

As shown in FIG. 11, after images on the front side of the seconddocument are read, a voltage is applied to the solenoid 22 and theejection roller 8 allows the second document to be transported. Thefirst document is also transported. Although the first document passesthrough the reading position R, image reading on the first document isnot performed at this time.

Then, as shown in FIG. 12, the solenoid 22 is released by the time theleading end of the first document reaches the ejection roller 8. Afterthe trailing end of the first document passes through the readingposition R, a voltage is applied to the solenoid 22 again, and the firstdocument is ejected onto the paper ejection tray 21.

Finally, as shown in FIG. 13, upon completion of the image reading onthe back side of the second document, the idle transport of the seconddocument is performed, and the second document is ejected onto the paperejection tray 21. The operations in high-speed double-side reading modeare thus completed.

In the present embodiment, the inter-sheet correction processor 1304 ofthe reader 200 performs a light-distribution fluctuation correctionprocess and dust correction process as inter-sheet correctionprocessing.

FIG. 14 is a block diagram showing exemplary the light-distributionfluctuation correction process and the dust correction process in theinter-sheet correction processor 1304 of the reader 200. Duringintervals between individual documents being transported, the CCD sensor208 reads a reference white plate at the reading position R. Inter-sheetcorrection processing is thus performed on the basis of the readwhite-level data. A light-distribution fluctuation correction process1501 and a dust correction process 1502 that constitute the inter-sheetcorrection processing performed during the intervals between documentsbeing transported will now be described.

The light-distribution fluctuation correction process 1501 includeslight-intensity fluctuation correction 1503 in which the light intensityof the lamp 203 in the scanner unit 209 is corrected, and lightdistribution correction 1504 in which light distribution patterns in themain scanning direction are corrected. The light intensity of the lamp203 gradually decreases with increasing illuminating time. Therefore, asshown in FIG. 15, the light-intensity fluctuation correction 1503 isperformed to increase the overall level of light intensity of the lamp203 from the current level to the target level. Like the lightintensity, the light distribution of the lamp 203 in the main scanningdirection changes with time. Therefore, as shown in FIG. 16, the lightdistribution correction 1504 is performed so that the light distributionin the main scanning direct is kept at the same light-intensity level(constant level).

The dust correction process 1502 is the correction of dust at thereading position R, and involves dust detection 1505, dust counting1506, and dust removal 1507. The dust detection 1505 is an operation, atthe reading position R, for detecting dust present in the main scanningdirection. As shown in FIG. 17, pixels below a dust criterion aredetected as dust pixels. The dust counting 1506 is an operation forcounting the number of dust spots detected through the dust counting1506. In FIG. 17, dust pixels are detected at three points. As shown inFIGS. 18A and 18B, the dust removal 1507 is an operation for making dustless noticeable by interpolation of adjacent pixels.

The processing can start and end at any of the above-describedoperations. Each operation can create correction data upon completion.By performing the above-described correction processing in the intervalsbetween documents, the inter-sheet correction processor 1304 creates theinter-sheet correction data 1508 and sets the inter-sheet correctiondata 1508 for the correction circuit 1403 in the image processor 1302 sothat image reading on documents can be performed.

Next, inter-sheet correction scheduling and a method for itsimplementation, according to the present embodiment, will be described.To transport a document from the position of the first registrationroller 3, the interval between the document and the previous document isnormally calculated with reference to the registration sensor 11. Thedocument is thus transported on the basis of this calculation.

In image reading in high-speed double-side reading mode, the calculationof the interval between the back side of the first document (n-th sheet)and the front side of the second document ((n+1)-th sheet) is performedin the same manner. However, in FIG. 10 to FIG. 11, the interval betweenthe completion of image reading on the front side of the second document((n+1)-th sheet) and the arrival of the reversed first document (n-thsheet) may be shorter than normal, as the reversed first document is nottransported on the basis of the calculation of the interval as describedabove. Since a predetermined time period required for thelight-distribution fluctuation correction process and the dustcorrection process may not be ensured in such a case, scheduling forinter-sheet correction processing is performed as described below.

A method for calculating an inter-sheet period T that can be used as areference for performing inter-sheet correction processing in intervalsbetween documents will now be described.

FIG. 19 is a diagram for explaining the calculation of inter-sheetperiods. Document A is shown currently passing through the readingposition R. The read sensor 12 is turned off after detecting the passageof the document A. Time T that elapses from when the read sensor 12 isturned off to when the read sensor 12 detects the next document B and isturned on is measured. Since document A and document B are transportedat the same speed in the vicinity of the reading position R, time thatelapses from when the trailing end of the previous document A passesthrough the reading position R to when the leading end of the document Breaches the reading position R is equal to the time T described above.Therefore, inter-sheet correction is performed with reference to thetime T (hereinafter called inter-sheet period T).

The inter-sheet period T varies depending on the reading mode(single-side reading mode, normal double-side reading mode, orhigh-speed double-side reading mode), and depending on the reading faceof the document. Therefore, the inter-sheet correction processor 1304measures (calculates), in advance, the inter-sheet period T inadjustment mode or the like, and stores each inter-sheet period T in theinter-sheet correction processor 1304 so that each inter-sheet period Tcan be immediately referred to when a reading mode is set.

That is, in single-side reading mode, the inter-sheet period is alwaysT1. In normal double-side reading mode, the inter-sheet period is T2(front side→back side), T3 (back side→reversed document), or T4(reversed document→front side of the next document) . In high-speeddouble-side reading mode, the sequence of passage of documents is asfollows: n-th sheet (back side)→(n+1)-th sheet (front side)→n-th sheet(reversed document)→(n+1)-th sheet (back side)→(n+2)-th sheet (frontside)→(n+1)-th sheet (reversed document)→. . . . Therefore, inhigh-speed double-side reading mode, the inter-sheet period is T6 (n-thsheet (back side)→(n+1)-th sheet (front side)), T7 ((n+1)-th sheet(front side)→n-th sheet (reversed document)), or T8 (n-th sheet(reversed document) →(n+1)-th sheet (back side)).

Next, as an inter-sheet correction scheduling method of the presentembodiment, a method for dividing the processing of thelight-distribution fluctuation correction process and dust correctionprocess into multiple steps by time period, and a method for schedulingthe sequence of the steps will be described.

FIG. 20 shows an example in which the processing of thelight-distribution fluctuation correction process and dust correctionprocess is divided into multiple steps by time period. In the presentembodiment, as described above (see FIG. 14), the light-distributionfluctuation correction process is divided into the light-intensityfluctuation correction (step 1) and the light distribution correction(step 2). The dust correction process is divided into the dust detection(step 3), the dust counting (step 4), and the dust removal (step 5).

Moreover, as described above, the inter-sheet correction processor 1304stores the inter-sheet periods for each of the reading modes(single-side reading mode, normal double-side reading mode, andhigh-speed double-side reading mode) therein. The inter-sheet correctionprocessor 1304 determines the minimum inter-sheet period from theplurality of inter-sheet periods that are stored therein. Theinter-sheet correction processor 1304 selects the minimum inter-sheetperiod from all the inter-sheet periods stored. Then, as shown in FIG.21, the inter-sheet correction processor 1304 performs the scheduling ofthe steps 1 to 5 on the basis of the minimum inter-sheet period, withrespect to each reading mode.

FIG. 21 shows an example of a schedule pattern table in which theinter-sheet correction processing (light-distribution fluctuationcorrection process and dust correction process) is divided into multiplesteps on the basis of the minimum inter-sheet period. “n” (1, 2, 3, and4) represents a correction processing unit divided by time period. Thatis, “n” represents a unit of correction processing to be performedduring one inter-sheet period, and “max” represents the maximum numberof processing steps for performing all the steps of the inter-sheetcorrection processing. Since the minimum inter-sheet period variesdepending on the reading mode, the maximum number of correctionprocessing units (max) also varies depending on the reading mode. Themaximum numbers of correction processing units in single-side readingmode, normal double-side reading mode, and in high-speed double-sidereading mode are three, two, four, respectively. The entire inter-sheetcorrection processing is completed by performing all the steps in everycorrection processing unit. Then, the inter-sheet correction processingin FIG. 22 and FIG. 23 is performed on the basis of the schedule patterntable in FIG. 21.

In single-side reading mode, where the maximum number of correctionprocessing units is three, the steps are assigned as follows:

-   1. Execute steps 1 and 2 in the first correction processing unit    (n=1).-   2. Execute steps 3 and 4 in the second correction processing unit    (n=2).-   3. Execute step 5 in the third correction processing unit (n =3).

In normal double-side reading mode, where the maximum number ofcorrection processing units is two, the steps are assigned as follows:

-   1. Execute steps 1 to 4 in the first correction processing unit 1    (n=1).-   2. Execute step 5 in the second correction processing unit 2 (n=2).

In high-speed double-side reading mode, where the maximum number ofcorrection processing units is four, the steps are assigned as follows:

-   1. Execute step 1 in the first correction processing unit 1 (n=1).-   2. Execute step 2 in the second correction processing unit (n=2).-   3. Execute steps 3 and 4 in the third correction processing unit    (n=3).-   4. Execute step 5 in the fourth correction processing unit (n=4).

FIG. 22 and FIG. 23 are flowcharts showing exemplary inter-sheetcorrection processing. First, the inter-sheet correction processor 1304sets a reading mode for an image reading job selected through theoperating section by a user (step S301). According to the reading mode,the inter-sheet correction processor 1304 determines a schedule patternfor the inter-sheet correction processing on the basis of the schedulepattern table in FIG. 21 (step S302). Then, the reader 200 startsreading images from a document (step S303), and the inter-sheetcorrection processor 1304 determines whether or not the trailing end ofthe document has passed through the reading position R (step S304).

If it is determined that the trailing end of the document has passedthrough the reading position R, the inter-sheet correction processor1304 determines whether or not the end of the image reading job has beenreached (step S305). If the end of the image reading job has not beenreached, the inter-sheet correction processor 1304 starts performing theinter-sheet correction processing in the n-th correction processing unitaccording to the schedule pattern corresponding to the reading mode(step S306). For example, in high-speed double-side reading mode, thesteps in the first to fourth correction processing units (n=1 to 4) areperformed.

Then, referring to FIG. 23, the inter-sheet correction processor 1304determines whether or not the inter-sheet correction processing in then-th correction processing unit has been completed (step S307). Ifcompleted, the inter-sheet correction processor 1304 increments n by one(n=n+1) (step S308). Next, the inter-sheet correction processor 1304determines whether or not n has exceeded the maximum number ofcorrection processing units (max) (step S309). If n has exceeded themaximum number of correction processing units (max), the inter-sheetcorrection processor 1304 assigns zero to n in order to start over theinter-sheet correction processing (step S311). Upon completion of theinter-sheet correction processing, image reading for the next documentis enabled (step S310).

On the other hand, if the inter-sheet correction processing in the n-thcorrection processing unit has not been completed (“NO” in step S307),the inter-sheet correction processor 1304 determines whether or not theleading end of the next document has reached the reading position Rbefore the completion of the inter-sheet correction processing (stepS312). If the read sensor 12 detects that the inter-sheet period isshort and that the leading end of the next document has reached thereading position R before the completion of the inter-sheet correctionprocessing, the inter-sheet correction processor 1304 issues a stopcommand. Then, the inter-sheet correction processor 1304 determineswhether or not a stop command has been issued (step S312). If a stopcommand has not been issued, the inter-sheet correction processor 1304continues performing the inter-sheet correction processing. On the otherhand, if it is determined that a stop command has been issued, theinter-sheet correction processor 1304 stops performing the inter-sheetcorrection processing in the n-th correction processing unit (step S313)and starts reading images from the next document (step S310). Theprocessing described above is repeated until the end of the imagereading job.

Accordingly, with respect to the present embodiment described above, theinter-sheet correction processing is divided into steps by time period,on the basis of the inter-sheet period according to each of the readingmodes (single-side reading mode, normal double-side reading mode, andhigh-speed double-side reading mode). Then, the scheduling of the stepsin the inter-sheet correction processing is performed with respect toeach reading mode. Since the inter-sheet correction processing can thusbe performed even if the intervals between individual documents beingtransported are reduced in high-speed double-side reading mode or thelike, the degradation in read images can be prevented.

Second Exemplary Embodiment

The second embodiment of the present invention differs from the firstembodiment in that an inter-sheet correction scheduling method shown inFIG. 24 and FIG. 25 is executed. The other components of the presentembodiment will not be described here, as they are similar to theircorresponding components of the first embodiment (FIGS. 1, 3, 4 and 5).

As an inter-sheet correction scheduling method of the presentembodiment, a method for scheduling the sequence of thelight-distribution fluctuation correction process and dust correctionprocess will be described.

As described above, in high-speed double-side reading mode, the intervalbetween reading images on the back side of the n-th document and thefront side of the (n+1)-th document is calculated, as normal, withreference to the registration sensor 11. However, as described above,the interval between the completion of image reading on the front sideof the (n+1)-th document and the arrival of the reversed n-th documentmay be shorter than normal. In the high-speed double-side reading mode,documents are transported in the order as follows: n-th sheet (backside) →(n+1)-th sheet (front side)→n-th sheet (reverseddocument)→(n+1)-th sheet (back side)→(n+2)-th sheet (frontside)→(n+1)-th sheet (reversed document)→. . . . Therefore,determination as to whether or not the period until the arrival of thenext document will be short can be made by observing the sequence ofdocuments passing through the reading position R. If the interval isshort, the light-distribution fluctuation correction process or the dustcorrection process is sequentially performed.

FIG. 24 and FIG. 25 are flowcharts showing exemplary inter-sheetcorrection processing in high-speed double-side reading mode. First, theinter-sheet correction processor 1304 sets the high-speed double-sidereading mode as a reading mode for an image reading job selected throughthe operating section by the user. The inter-sheet correction processor1304 sets the light-distribution fluctuation correction process asdefault processing to be performed when the intervals between individualdocuments transported by the ADF 100 is short (step S401). Then thereader 200 starts reading images from a document (step S402), and theinter-sheet correction processor 1304 determines whether or not thetrailing end of the document has passed through the reading position R(step S403). If it is determined that the trailing end of the documenthas passed through the reading position R, the inter-sheet correctionprocessor 1304 determines whether or not the end of the image readingjob has been reached (step S404).

Referring to FIG. 5, if the end of the image reading job has not beenreached (if the next document is present), the inter-sheet correctionprocessor 1304 determines whether or not the inter-sheet period forperforming the inter-sheet correction processing is short (step S405).As described above, this can be determined on the basis of the readingmode and by observing the sequence of documents passing through thereading position R.

If the length of the inter-sheet period is normal, the inter-sheetcorrection processor 1304 performs the light-distribution fluctuationcorrection process and the dust correction process (step S406 and stepS407) and starts reading images on the next document (page) (step S408).If the inter-sheet period is short, the inter-sheet correction processor1304 determines which of the light-distribution fluctuation correctionprocess and the dust correction process is to be performed as the nextprocessing (step S409). If the next processing is the light-distributionfluctuation correction process (if the light-distribution fluctuationcorrection process is set as the default processing), the inter-sheetcorrection processor 1304 starts performing the light-distributionfluctuation correction process (step S413).

Then, the inter-sheet correction processor 1304 determines whether ornot the light-distribution fluctuation correction process has beencompleted (step S414). If the read sensor 12 detects that theinter-sheet period is short and that the leading end of the nextdocument has reached the reading position R before the completion of thelight-distribution fluctuation correction process, the inter-sheetcorrection processor 1304 issues a stop command. If thelight-distribution fluctuation correction process has not beencompleted, the inter-sheet correction processor 1304 determines whetheror not a stop command has been issued (step S415).

Referring back to FIG. 24, if a stop command has been issued, theinter-sheet correction processor 1304 stops the light-distributionfluctuation correction process and sets light-distribution fluctuationcorrection process as the next processing (step S419). On the otherhand, if a stop command has not been issued, the inter-sheet correctionprocessor 1304 waits for the completion of the light-distributionfluctuation correction process and sets dust correction process as thenext processing (step S418).

Referring back to FIG. 25, if on the other hand, the next processing isdust correction process (“NO” in step S409), the inter-sheet correctionprocessor 1304 starts performing the dust correction process (stepS410). Then, the inter-sheet correction processor 1304 determineswhether or not the dust correction process has been completed (stepS411). If the inter-sheet period is short and the leading end of thenext document has reached the reading position R before the completionof the dust correction process, the inter-sheet correction processor1304 issues a stop command. Then, the inter-sheet correction processor1304 determines whether or not a stop command has been issued (stepS412).

Now referring back to FIG. 24, if a stop command has been issued (stepS415), the inter-sheet correction processor 1304 stops performing thedust correction process and sets dust correction process as the nextprocessing (step S418). On the other hand, if a stop command has notbeen issued, the inter-sheet correction processor 1304 waits for thecompletion of the dust correction process and sets light-distributionfluctuation correction process as the next processing (step S419). Then,the inter-sheet correction processor 1304 starts reading images on thenext document (page) (step S420). The processing described above isrepeated until the end of the image reading job.

Accordingly, in the present embodiment described above, even if theinterval between reading images from individual documents is reduced inhigh-speed double-side reading mode, the inter-sheet correctionprocessing is performed as much as possible by scheduling it. Thisprevents degradation in the quality of images read from the nextdocument.

Other Exemplary Embodiments

The image reading apparatus of the first and second embodiments has astructure in which the ADF and the reader are separate. The presentinvention is not only applicable to image reading apparatuses having thestructure described above, but also applicable to image readingapparatuses that integrate an ADF with a reader.

While the image reading apparatus is described in the first and secondembodiments, the present invention is not only applicable to the imagereading apparatus described above, but also applicable to image formingapparatuses (e.g. copier, multi-function machine, and facsimile machine)that incorporate the image reading apparatus.

Moreover, the present invention is achieved by supplying, to a system orapparatus, a storage medium (recording medium) on which a softwareprogram code for performing the functions of the above-describedembodiments is recorded. In other words, the present invention isachieved when a computer (CPU or micro-processing unit (MPU)) in thesystem or apparatus reads and executes the program code stored in thestorage medium.

In this case, the program read out of the storage medium performs thefunctions of the above-described embodiments, and thus the storagemedium on which the program code is recorded constitutes the presentinvention.

In addition to the case where the functions of the above-describedembodiments are performed when the computer reads and executes theprogram code, there are other cases where the functions of theabove-described embodiments are performed. For example, on the basis ofinstructions of the program code, an operating system (OS) running onthe computer carries out all or a part of the actual processing, whichallows the functions of the above-described embodiments to be performed.

The functions of the above-described embodiments are also performed whenthe program code read out of the storage medium is written in a functionexpansion card in a computer, or in a memory of a function expansionunit connected to a computer. For example, after the program code iswritten, the function expansion card or a CPU in the function expansionunit carries out, on the basis of instructions of the program code, allor a part of the actual processing, which allows the functions of theabove-described embodiments to be performed.

The program code described above may take any form that allows acomputer to perform the embodiments of the present invention. Examplesof such a form include an object code, a program to be executed by aninterpreter, and script data to be supplied to an OS.

A recording medium for supplying the program code may take any form thatallows the program code to be stored thereon. Examples of such arecording medium include a random-access memory (RAM), a nonvolatile RAM(NV-RAM), a floppy (registered trademark) disk, an optical disk, amagneto-optical (MO) disk, a compact-disk read-only memory (CD-ROM), aCD-recordable (CD-R), a CD-rewritable (CD-RW), a digital versatile disk(DVD) (e.g. a DVD-ROM, a DVD-RAM, a DVD-RW, and a DVD+RW), a magnetictape, a nonvolatile memory card, and other types of ROMs. Alternatively,the above-described program code may be downloaded from a computer ordatabase (not shown) connected to the Internet, a commercial network, orto a local area network (LAN).

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures and functions.

1. An image reading apparatus configured to allow a reading device fixedat a reading position to read images from a document while transportingthe document, the image reading apparatus comprising: a correcting unitadapted to perform correction processing associated with image readingperformed by the reading device; a calculating unit adapted to calculatea time interval from one document to another document that is beingtransported; a scheduling unit adapted to divide the correctionprocessing into a plurality of steps and schedule execution of theplurality of steps based on the time interval calculated by thecalculating unit; and an executing unit adapted to sequentially executethe plurality of steps scheduled by the scheduling unit in accordancewith a document passing through the reading position.
 2. The imagereading apparatus according to claim 1, wherein there are a plurality ofreading modes, including, a single-side reading mode in which one sideof a document is read, a normal double-side reading mode in which bothsides of a document are read, and a high-speed double-side reading modein which, after a back side of a first document is read, a front side ofa subsequent document is read simultaneously with a reverse ejection ofthe first document.
 3. The image reading apparatus according to claim 1,wherein the correction processing to be performed is selected from agroup of operations including, an operation for correcting fluctuationsin an intensity of light illuminating a document, an operation forcorrecting light distribution, an operation for detecting dust at thereading position, an operation for counting dust spots to obtain anumber that represents a quantity of dust spots, and an operation forcorrecting pixels in which dust has been detected.
 4. The image readingapparatus according to claim 1, further comprising a detecting unitadapted to detect that a document has passed through the readingposition, wherein the executing unit, during the execution of theplurality of steps scheduled by the scheduling unit, stops executing theplurality of steps when the detecting unit detects that a leading end ofa subsequent document has passed through the reading position.
 5. Theimage reading apparatus according to claim 2, wherein the schedulingunit assigns the plurality of steps to time units that can fall withintime intervals between documents transported during reading in theplurality of reading modes and creates a schedule table for each of theplurality of reading modes such that all the plurality of steps areexecuted within an arbitrary number of time intervals between documentsbased on the time intervals between documents transported during readingin the plurality of reading modes and based on time required for theexecution of the plurality of steps.
 6. The image reading apparatusaccording to claim 2, wherein the executing unit executes, according toa sequence scheduled by the scheduling unit, executable operations ofthe correction processing when a time interval between documents duringreading in the high-speed double-side reading mode is short.
 7. Theimage reading apparatus according to claim 1 further comprising asetting unit adapted to set a reading mode, wherein the calculating unitcalculates a time interval between documents according to a reading modeset by the setting unit.
 8. An image reading and forming apparatusconfigured to allow a reading device fixed at a reading position to readimages from a document while transporting the document, the imagereading and forming apparatus comprising: a correcting unit adapted toperform correction processing associated with image reading performed bythe reading device; a calculating unit adapted to calculate a timeinterval from one document to another document that is beingtransported; a scheduling unit adapted to divide the correctionprocessing into a plurality of steps and schedule execution of theplurality of steps based on the time interval calculated by thecalculating unit; an executing unit adapted to sequentially execute theplurality of steps scheduled by the scheduling unit in accordance with adocument passing through the reading position; and an image forming unitadapted to form an image on a sheet based on images read by the imagereading apparatus.
 9. A control method for an image forming apparatusallowing a reading device fixed at a reading position to read imagesfrom a document while transporting the document, the control methodcomprising: performing correction processing associated with imagereading performed by the reading device; calculating a time intervalfrom one document to a next document that are being transported duringreading in a selected reading mode; dividing the correction processinginto a plurality of steps and scheduling the execution of the pluralityof steps based on the calculated time interval; and sequentiallyexecuting, in accordance with a document passing through the readingposition, the plurality of scheduled steps.
 10. A computer readablemedium containing computer-executable instructions for an image formingapparatus allowing a reading device fixed at a reading position to readimages from a document while transporting the document, the computerreadable medium comprising: computer-executable instructions forperforming correction processing associated with image reading performedby the reading device; computer-executable instructions for calculatinga time interval from one document to a next document that are beingtransported during reading in a selected reading mode;computer-executable instructions for dividing the correction processinginto a plurality of steps and scheduling the execution of the pluralityof steps based on the calculated time interval; and computer-executableinstructions for sequentially executing, in accordance with a documentpassing through the reading position, the plurality of scheduled steps.